This invention relates to a new and distinctive mandarin cultivar designated ‘DaisySL’, which was developed at Riverside, Calif. and derived from an irradiated bud of ‘Daisy’ mandarin. ‘Daisy’ mandarin was produced in Indio, Calif. in 1963 by J.R. Furr from a conventional hybridization of 2n ‘Fortune’ x 2n ‘Fremont’ mandarin. ‘Fortune’ mandarin was itself produced from a conventional hybridization of 2n ‘Clementine’ x 2n ‘Dancy’ mandarin made by J.R. Furr in Indio, Calif. in 1954 and released in 1964. ‘Fremont’ mandarin was obtained from a conventional hybridization of 2n ‘Clementine’ mandarin x 2n ‘Ponkan’ mandarin made by P.C. Reece in Orlando, Fla. in 1948 and later fruited, selected and released by J.R. Furr in Indio, Calif. in 1964.
Irradiation of budwood from registered ‘Daisy’ trees in Lindcove, Calif. was accomplished in June, 1997 at Riverside. Two hundred buds of ‘Daisy’ were irradiated as follows: 50 buds were irradiated using 50 Gray units of gamma irradiation from a Cobalt-60 irradiation source; 100 buds were irradiated at 30 Gray units and 50 buds were irradiated at 40 Gray units. Buds from this irradiation were propagated onto various rootstocks in greenhouses at Riverside and Lindcove where they were grown to field-plantable-sized trees. Out of these irradiations, a total of 80 trees were obtained. This low yield of trees is typical because the radiation kills many of the buds. These trees were planted in 1998 at Riverside (28 trees) and Lindcove Research and Extension Center (52 trees). Fruit production and evaluation began in 2001. Only one selection from this irradiated population (propagated on Carrizo citrange rootstock) distinguished itself from the others in having very low seed counts in comparison to the original ‘Daisy’ cultivar, and with the excellent fruit quality and normal fruit production characteristics of the ‘Daisy’ parent. Although another tree from the irradiated population had fruit having a lower seed number than the ‘Daisy’ parent, the fruit had a higher mean seed count and were smaller than the selected variety. After two seasons of fruiting this selection, designated as ‘Daisy IR1’, was selected for further trials and in January 2003 buds were taken and propagated onto Carrizo and C35 citrange rootstock. Budwood was also sent in April 2003 for evaluation of disease status and elimination of viruses and other pathogens as needed to establish trial plantings. ‘DaisySL’ was known throughout experimental evaluation as Daisy IR1 (for DAISY IRradiated selection #1). Twenty trees were planted at Riverside in June 2003. Fruit production on these 20 trees commenced in 2006. In June 2004 two trees of ‘DaisySL’, which had been produced from budwood that had tested and certified as tristeza-free, were sent Lindcove, Calif. where they were planted in the citrus breeding block. In June 2004 seventy-two trees, produced in Lindcove, Calif. were planted (twelve trees each) at six sites, Arvin, Irvine, Lindcove, Oasis, Santa Paula and Woodlake, Calif. All trials were propagated equally on Carrizo and C35 citrange rootstocks. Fruit production of these propagated trees commenced in 2006 (a few trees at each site) and 2007 (all trees at all sites). The properties of ‘DaisySL’ were found to be true to type and transmissible by asexual reproduction in comparing these plantings with the original ‘DaisySL’ selection.